\documentclass{article}

\usepackage[square,sort,comma,authoryear]{natbib}

\usepackage{url}                  % format URLs

\begin{document}

citet example: \citet{Test:Book,Test:Inproceedings,Test:Article}.


ctanchor\,\citep{Test:Book,Test:Inproceedings,Test:Article}.


citet example: \citet{Test:Book}.


ctanchor\,\citep{Test:Book}.


citet example: \citet{Test:Book,Test:Inproceedings}.


ctanchor\,\citep{Test:Inproceedings,Test:Article}.


\bibliographystyle{abbrvnat}
\bibliography{references}

\end{document}
